AUSTRALIAN drinking water standards are under scrutiny after
scientific research linking commonly used herbicides to gender
bending in male frogs.

The National Health and Medical Research Council is to reassess
its drinking water guidelines after minuscule traces of the
herbicides atrazine and simazine were found to turn the frogs
into hermaphrodites  creatures with male and female sex
organs.

Australian guidelines allow up to 40 parts per billion (ppb)
of atrazine in drinking water before it is considered a health
risk.

But scientific studies have found that male frogs grow ovaries
when exposed to the chemical at the minuscule level of .1ppb
in water.

"The current Australian Drinking Water Guidelines specify
that atrazine should not be detected in drinking water and that
if it is detected, then remedial action should be taken to stop
contamination," NHMRC spokesman Nigel Harding said.

"The guidelines state that if present in drinking water,
atrazine would not be a health concern in humans unless the
concentration exceeds 40ppb.

"The guidelines are currently under review."

Atrazine, which was banned across the European Union in 2003,
has been used for weed control in Australia for more than 25
years and is the nation's second most commonly used agricultural
pesticide, being sprayed around canola fields, forestry plantations
and sugar cane crops.

There is no legal requirement for atrazine users to notify water
authorities when the chemical is being sprayed.

No traces have been found in Melbourne's drinking water since
testing began in 2005, but Melbourne Water acknowledges it probably
is used in the city's unprotected water catchments.

But while Melbourne Water tests twice yearly for atrazine to
a level of .5ppb, it does not test for its close chemical relative
simazine, which is used on Yarra Valley vineyards.

The Yarra Valley is part of the catchment zone for the Sugarloaf
reservoir, which supplies drinking water to the northern and
western suburbs.

"Melbourne Water understands that simazine is used infrequently
in the Yarra Valley, and because of this infrequency of use
and its degradation in the environment, testing is not conducted,
consistent with our risk assessments," a Melbourne Water
spokesman said.

At .5ppb, its atrazine tests are still five times higher than
the level required to turn male frogs into hermaphrodites, according
to US scientist Dr Tyrone Hayes, an associate professor of integrative
biology at the University of California.

"What struck us as unbelievable was that atrazine could
cause such dramatic effects at such low levels," said Dr
Hayes, an associate professor of integrative biology at the
University of California, Berkeley, who led the frog study.

"If you take five grains of salt, divide this weight by
5000, that is the amount of atrazine that causes these abnormalities."
Environmentalists say Melbourne Water's tests do not go far
enough.

"They now test for atrazine twice a year at each of their
testing locations, that's two readings per year or one reading
every 182 days," said Anthony Amis of Friends of the Earth,
which partly sponsored a visit to Australia by Dr Hayes.

"Their results only go as low as .5ppb, which means they
probably won't detect atrazine at the level required."